1. Technical Field
Embodiments of the present disclosure relate to phones, and especially to a subscriber line interface circuit (SLIC) of a phone.
2. Description of Related Art
A subscriber line interface circuit (SLIC) is operable to connect subscribers and switches. However, noise, such as crosstalk, may occur when many subscribers use the SLIC at the same time.
FIG. 4 shows technical standards of the Nippon Telegraph and Telephone Corporation (NTT). A difference value between a ring wire and a tip wire should sustain approximately 48V when a phone is in an on hook state. As shown for the SLIC, the phone is in a constant voltage mode and the difference value between the tip wire and ring wire is generally 48V, when the phone is in the on hook state. The phone is in a constant current mode and a current value is generally 22 mA, when the phone is in an off hook state. The ring wire and the tip wire generate oscillatory voltages when the phone is in a pulse dialing state, that is, the tip wire and the ring wire will alternate operation between the constant voltage and the constant current, when the phone is in the pulse dialing state. Therefore, the phone may generate crosstalk and disturb neighboring connections.